Method and device for producing structural elements from a deep drawing blank

ABSTRACT

A method for producing components from a blank ( 1 ) made of a reshapable material, particular steel, in which the blank ( 1 ) is supported by a fluid cushion (F) against a shaping tool ( 5 ) during the deformation, and a device particularly intended for performing this method are disclosed. In the course of the method, the blank ( 1 ) is reshaped into an intermediate shape using the tool ( 5 ). Subsequently, the blank ( 1 ) deformed into the intermediate shape is locally deformed using a counter mold piece ( 6 ) which is moved against the blank ( 1 ) against the action direction (R) of the tool ( 5 ). In this way, exactly shaped components may be produced cost effectively without the danger of reduction in quality.

[0001] The present invention relates to a method for producing components from blank made of a reshapable material, particularly steel, in which the blank is supported against a shaping tool by a fluid cushion during the deforming. In addition, the present invention relates to a device which is particularly suitable for performing such a method. These types of devices typically have a receptacle into which a fluid, for example water or a comparable liquid, is poured as an action medium. A blank is held over the opening of the receptacle by suitable mechanisms, so that, for example, it may be deformed by a stamp which is positioned in the opening and movable into the receptacle. In this case, during the deforming, the fluid contained in the receptacle supports the blank as a cushion against the pressure exercised by the stamp, so that the blank takes on the shape predetermined by the stamp as the stamp progresses.

[0002] In an alternative method of the type initially described, the blank is pressed against a stationary tool, which is positioned in or over the receptacle opening, by elevating the pressure exercised by the fluid contained in the receptacle, through which the shape of the workpiece to be produced is determined. Combinations of the methods described are also in use.

[0003] Methods and devices of the type described above are suitable for the production of complex components having improved properties. In this case, the advantage of deforming performed with the aid of a cushion formed by a flowing action medium is that, unlike in typical deep drawing, in which a stamp deforms the blank in a matrix forming the countermold, the flowing of the material into the final shape is made easier. However, it is problematic that very high pressures are necessary for exact implementation of the desired component shape. Therefore, calibration of the preshaped component occurs at the end of the reshaping procedure in the conventional method, during which the shaping precision is elevated by a strong increase in pressure in the fluid cushion.

[0004] The production of “additional form elements”, which have small radii, has been shown to be particularly problematic in practice. These types of additional form elements may only be shaped into the component after the blank is deformed into the main shape of the component.

[0005] The high calibration pressures necessary for shaping the additional form elements lead to large forces, particularly in large area components, which are necessary for holding the blank in the respective device during the deforming procedure. Both the outlay for apparatus necessary for this purpose and the technical outlay which must be made for producing the high calibration pressures and for sealing the overall system which has these high pressures applied to it leads to high costs for the provision and operation of devices of the type discussed.

[0006] Reducing this outlay by mounting fixed counter mold pieces in the receptacle of the respective device, corresponding to the conventional deep drawing deformation of blanks, has been attempted. The blanks are pressed against these static, fixed counter mold pieces in the course of the movement performed by the tool, so that the implementation of the respective additional form elements is forced. This method has the disadvantage that the rigid counter mold elements in the receptacle engage in the reshaping at the time in which the main material flow has not yet ended and therefore uncontrolled material flow may be caused. This may in turn lead to overshoot edges, local damage to the surface, and sink marks, which reduce the quality of the components produced.

[0007] The object of the present invention is to provide a method and a device of the type described above, using which exactly shaped components may be produced cost effectively without the danger of reduction in quality.

[0008] This object is achieved, on one hand, by a method for producing components in which a blank made of a reshapable material, particularly steel, is supported by a fluid cushion against a shaping tool during the deforming and the following steps are completed:

[0009] deforming of the blank into an intermediate shape using the tool and

[0010] subsequent localized deforming of the blank, which is deformed into the intermediate shape, using a counter mold piece, which is moved against the blank against the action direction of the tool.

[0011] According to the present invention, the reshaping of the blank is divided into at least two steps. In the first step, the main part of the deforming occurs in that the blank is reshaped using the tool enough that all basic elements of the component shape are essentially implemented. When this main deforming is finished, the additional form elements are produced.

[0012] In contrast to the related art, an actively movable and controllable counter mold piece is moved toward the blank for this purpose. Its dimensions are implemented in such a way that at each case a deformation of the blank occurs which is restricted to the region of the additional form element. Since the counter mold piece actively works against the blank, it acts like a shaping tool itself. In contrast, the tool causing the main deforming forms the “matrix”, on which the blank is shaped, during the implementation of the respective additional form element.

[0013] The advantage of the method according to the present invention, which has at least two parts, is that the main deforming is performed only against the pressure of the fluid cushion, uninfluenced by a fixed counter element. In this case, both the material flow and the shaping can be laid out in such a way that optimum conditions for the final shaping of the respective additional form elements are provided.

[0014] Therefore, additional form elements having complex shapes may be produced exactly without the extreme elevation in pressure still required in the related art being necessary for this purpose. Damage to the blank or flaws of the material distribution which interfere with the visual impression are very reliably avoided. As a consequence, components which meet the highest requirements may be produced from blanks in the way according to the present invention with reduced outlay for apparatus.

[0015] A embodiment of the present invention which allows a particularly expedient performance of the method according to the present invention is characterized in that the tool is a stamp which is adjustable in its position. Using a movable stamp tool of this type, which is positionable on the blank, the shape of the workpiece to be produced may be generated using high shaping precision, with optimum utilization of the supporting effect of the fluid cushion.

[0016] It is particularly advantageous if the localized deforming is first performed when the pressure in the fluid cushion has reached a minimum value. This minimum value of the pressure may be reached automatically in the course of the main deforming of the blank. If this is not the case, then a pressure state more favorable for implementing the respective additional form element may be produced by a supplemental increase in pressure in the fluid cushion. Depending on the course and complexity of the shaping of the additional form element, it may additionally be expedient, using the counter mold element, to vary the pressure of the fluid cushion during the deforming in relation to the previously existing pressure. The minimum pressure existing in the fluid cushion should preferably correspond in this case to the pressure at which shaping of the additional form element caused by the pressure of the fluid cushion begins.

[0017] The generation of a specific pressure state by the counter mold piece at the beginning and during the production of the additional form elements is used for further improvement of the work result. If the blank is supported against the shaping tool using a sufficiently high pressure, the danger of the occurrence of uncontrolled material flows during the shaping of the respective additional form element is reduced. Surface damage of the component may be reliably prevented in this way.

[0018] The shaping precision of the component produced according to the present invention may be elevated further if the pressure of the fluid cushion is elevated after reaching the final shape. This final elevation in pressure is used, like the calibration procedure typical in the conventional method, for the purpose of correcting changes of the main shape of the component generated by the shaping tool which may occur as a consequence of the production of the additional form element.

[0019] On the other hand, the object described above is achieved in regard to a device for producing components from a blank made of a reshapable material, particularly steel, which is equipped with a receptacle filled with a fluid, with a device for holding the blank over an opening of the receptacle, and with a shaping tool, which is positionable over an opening of the receptacle, in that at least one counter mold piece, which is movable against the blank against the action direction of the tool, is positioned in the receptacle. Such a device equipped with an actively adjustable counter mold piece is particularly suitable for performing the method according to the present invention because the counter mold piece is controllable in such a way that it only engages in the deforming procedure when the main deforming of the blank by the tool is finished. In this way, an extreme elevation in pressure, as is still necessary in the related art for implementing complex additional form elements, is no longer necessary during operation of a device implemented according to the present invention. Therefore, these types of devices may be produced and operated at lower costs.

[0020] A particularly high-capacity device of the type according to the present invention may be implemented if the tool is a stamp which is adjustable in its position.

[0021] A device according to the present invention is preferably equipped with a control unit which outputs a signal for adjusting the counter element against the blank as soon as a specific deformation of the blank is achieved. This embodiment of the present invention is particularly suitable for automated production of deep drawn components. In principle, it is conceivable in this connection that the appropriate signal for adjusting the counter piece is output, for example, as a function of the adjustment path of the shaping tool which has been covered. However, the control unit preferably outputs the signal for adjustment when the pressure of the fluid contained in the receptacle has exceeded a specific value which is favorable for the shaping of the additional form element.

[0022] In order to be able to adjust the pressure existing in the receptacle purposefully, a controllable valve is to be provided, using which the pressure in the receptacle is changeable. In addition, it is favorable if, in a device implemented according to the present invention, a pressure generation device is present, using which the pressure of the pressure [sic] contained in the receptacle may be elevated. A pressure state favorable for implementing the additional form element may be achieved purposefully using such a pressure generation device.

[0023] In the following, the invention is described in more detail with reference to a drawing which illustrates an exemplary embodiment. In schematic illustration:

[0024]FIG. 1 shows a device for producing a component from a blank in a first operating position in a longitudinal section;

[0025]FIG. 2 shows the device shown in FIG. 1 in a second operating position;

[0026]FIG. 3 shows the device shown in FIG. 1 in a third operating position;

[0027]FIG. 4 shows the device shown in FIG. 1 in a fourth operating position.

[0028] The device shown in the figures is used for producing, for example, a car body component from a blank 1, which is cut to size from thin sheet metal. For this purpose, the device includes a receptacle 2, which is implemented like a box and is open on top, a mechanism 4 for holding blank 1, which is implemented as a blank holder ring and may be placed on the upper edge 3 of receptacle 2, which surrounds the receptacle opening, and a stamp 5, forming a shaping tool, which may be introduced using an adjustment mechanism, not shown, in adjustment direction R into the opening of receptacle 2 from a rest position (FIG. 1) located above the receptacle.

[0029] In addition, there is a counter mold piece 6 in receptacle 2 carried by a piston 8, which is hydraulically adjustable in an adjustment direction S, directed against the adjustment direction R of the stamp, using an adjustment mechanism 7. A pressure generation device 9 is provided for filling receptacle 2 with a liquid F, for example water.

[0030] Stamp 5 has a shape on its side facing blank 1 which corresponds to the shape of the component to be produced from the blank. In this case, an additional form element N is implemented in a region A, at which two wall elements of the component to be produced, which run into one another nearly perpendicularly, merge into one another in a small radius. Counter mold piece 6, which is provided for producing this additional form element N and is positioned aligned with additional form element N in the vertical direction, has a shape corresponding to the counterpart of the shape of additional form element N on its side assigned to blank 1.

[0031] In the operating position illustrated in FIG. 1, stamp 5 and mechanism 4 are in their raised rest position, so that blank 1 may be laid unobstructed on edge 3 of receptacle 2. Counter piece 6 is simultaneously located in its starting position, directly neighboring the receptacle floor, in which the distance between blank 1 and counter piece 6 is greater than the stroke of stamp 5 performed during the deforming of blank 1. Receptacle 2 is filled with liquid F.

[0032] After the insertion of blank 1, mechanism 4 is lowered, so that the edge of blank 1 is held clamped over the receptacle opening between mechanism 4 and upper edge 3 of receptacle 2. Stamp 5 is brought into a position, starting from which the deformation of blank 1 is performed. Counter piece 6 is in its rest position, as before. If necessary, a pre-deforming of blank 1 is performed in the direction of stamp 5 at this time, in that the pressure of liquid F, which receptacle 2 is filled with, is elevated. In this way, the change in shape in the region of the center of the blank is elevated and material for the subsequent main deforming in the region of receptacle 2 is stockpiled (FIG. 2).

[0033] Subsequently, stamp 5 is introduced into the opening of receptacle 2 in adjustment direction R, so that blank 1 is deformed. At the same time, as a function of the steel material of blank 1 and/or the component shape to be produced, the holding forces exercised by mechanism 4 are dimensioned in such a way that, starting from the edge of blank 1, a material flow in the inside of receptacle 2 is allowed or the edge of blank 1 is held fixed. During the deforming of blank 1 by stamp 5, liquid F, with which receptacle 2 is filled, forms a fluid cushion, by which blank 1 is supported on its side facing away from stamp 5. Support pressure P in liquid F is controlled and/or regulated according to the progress of the deformation of blank 1 caused by stamp 5. At the end of the stroke path of stamp 5, blank 1 has obtained an intermediate shape in which all form elements of the component have reached their final shape except for additional form element N. The main deforming of blank 1 performed by stamp 5 is thus finished (FIG. 3).

[0034] To produce additional form element N, support pressure P is elevated by pressure generation mechanism 9 to a minimum value at which the shaping of additional form element N due to support pressure P exercised by liquid F just begins. However, further elevation in pressure does not occur at this time. Instead, counter mold piece 6 is now moved in adjustment direction S toward blank 1, so that blank 1 is drawn into the shape of additional form element N predetermined by stamp 5, which is at a standstill at this time (FIG. 4).

[0035] When the production of additional form element N is finished, support pressure P is elevated again in order to definitively calibrate the shape of blank 1 on stamp 5.

[0036] Finally, stamp 5, mechanism 4, and counter piece 6 are moved back into their starting position illustrated in FIG. 1, so that the finished component may be removed from the device.

[0037] List of Reference Numbers

[0038]1 blank

[0039]2 receptacle

[0040]3 edge of receptacle 2

[0041]4 mechanism for holding blank 1

[0042]5 stamp

[0043]6 counter mold piece

[0044]7 adjustment mechanism

[0045]8 piston

[0046]9 pressure generation mechanism

[0047] A region

[0048] F liquid

[0049] N additional form element

[0050] R adjustment direction

[0051] S adjustment direction 

1. A method for producing components from a blank (1) made of a reshapable material, particularly steel, in which the blank (1) is supported by a fluid cushion (F) against a shaping tool (5) during the deformation, comprising the following steps: deformation of the blank (1) into an intermediate shape using the tool (5) and subsequent localized deforming of the blank (1) deformed into the intermediate shape using a counter piece (6), which is moved against the blank (1) against the action direction (R) of the tool (5).
 2. The method according to claim 1, characterized in that the tool is a stamp which is adjustable in its position.
 3. The method according to claim 1 or 2, characterized in that the localized deformation is performed as soon as the pressure (P) in the fluid cushion (F) has reached a minimum value.
 4. The method according to claim 3, characterized in that the minimum value of the pressure (P) in the fluid cushion (F) corresponds to the pressure at which shaping of the additional form element (N) caused by the pressure of the fluid cushion (F) begins.
 5. The method according to one of the preceding claims, characterized in that the pressure (P) of the fluid cushion (F) is varied in relation to the previously existing pressure during the deforming using the counter mold piece (6).
 6. The method according to one of the preceding claims, characterized in that the pressure (P) of the fluid cushion (F) is elevated after reaching the final shape.
 7. A device for producing components from a blank (1) made of a reshapable material, particularly steel, having a receptacle (2) filled with a fluid, having a mechanism (4) for holding the blank (1) over an opening of the receptacle (2), and having a shaping tool (5) which is positionable in the region of the opening of a receptacle (2), characterized in that at least one counter mold piece (6), which is movable against the blank (1) against the action direction (R) of the tool (5), is positioned in the receptacle (2).
 8. The device according to claim 7, characterized in that the shaping tool is a stamp (5) which is adjustable in its position.
 9. The device according to claim 7 or 8, characterized by a control unit which outputs a signal for adjusting the counter mold piece (6) against the blank (1) as soon as a specific deformation of the blank (1) is achieved.
 10. The device according to claim 7 or 8, characterized in that the control unit outputs the signal for adjustment as soon as the pressure (P) of the fluid contained in the receptacle (2) has exceeded a specific value.
 11. The device according to one of claims 7 to 10, characterized by a controllable valve, using which the pressure (P) in the receptacle (2) is changeable.
 12. The device according to one of claims 7 to 11, characterized by a pressure generation mechanism (9), using which the pressure (P) of the pressure (P) contained in the receptacle (2) may be elevated.
 13. A use of a device according to one of claims 7 to 12 for performing the method according to one of claims 1 to
 6. 